A short guide to building an AI agent harness from scratch in three modules
omarsar0 · x · 2026-09-15
- Elvis Saravia (omarsar0) shares a beginner path for building an agent harness from scratch, and suggests feeding the guide straight to your agent.
- Core advice: to really learn harnesses, implement a minimal one yourself in a language you like (TypeScript or Python). He hand-built his first one from Google's ReAct paper; today you can have your agent read the paper and generate a minimal, inspectable implementation.
- Target three parts:
- LLM module: handles all inference, ideally multi-model (he used OpenRouter); system prompt can live here or be split out if you want to explore context engineering.
- Tools module: recommended to build tools in a structured way (post truncated here).
Related event: Build your own agent harness from scratch: a minimal three-module guide(3 posts)→
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